why do mirrors lie?

[clive_murray_white]

<p>I took this selfie in a dark reflective surface the other day expecting it to confuse my camera into over exposing it but instead it got it right. I thought the camera's metering system would "think" it was looking at mid grey - So now I'm confused!</p>

<p>It also made me think about focus, f4 with lens at 72mm, sure I understand that DoF would mean that something would be in focus and others wouldn't but I get the feeling that the mirrored surface accelerated shallow DoF - or is this just my imagination?</p>

<p><img src="https://fbcdn-sphotos-f-a.akamaihd.net/hphotos-ak-xap1/t1.0-9/10536916_802453453120705_8157036460424000289_n.jpg" alt="" width="774" height="850" /></p>

[ellis_vener_photography]

It used to be that camera meters were dumb machines which assumed your goal was an exposure that balanced

highlights and shadow areas to achieve a "middle gray" overall balance. About 25 years ago, evaluative type TTL meters

in cameras began to become relatively more intelligent and that trend has continued. They now make assumptions like

"dark tones predominate in this scene, the photographer probably is doing that intentionally so I will respond that way

too."

 

To your confusion about mirrors and apparent extra and unexpected depth of focus. The camera looks like it is focusing

on you and not the mirror surface. Since you are shooting directly into the mirror, if you are five feet from the mirror the

camera is actually focusing on a point that is ten feet away. The greater the subject to camera "focus" distance, the

greater the apparent depth of focus is at any given aperture, no matter what your chosen aperture is.

[clive_murray_white]

<p>Thanks Ellis - I often click "auto tone" in Lightroom just to see what its suggestion may be - in scenes like the one above it invariably lightens things a lot - pity it's not as smart as the camera!</p>

<p>So if I want almost everything in focus in the mirror, I'll probably have to enter into the world of focus stacking.............</p>

[ellis_vener_photography]

...or put the camera on a tripod and stop way down, or a combination of the two approaches.

[lornesunley]

<p>Like Elllis said, use a tripod, stop down, set a fixed ISO, play with the shutter speed until you get what you want, use manual focus on the lens and set the focus on twice your distance from the mirror</p>

[bgelfand]

<p>Why? Because your light meter assumes an 18% reflectivity grey card. The mirror reflects about 95%+ of the light. The meter stops the camera down as if the scene were only 18% reflection and you are under exposed. If you look at the background, it looks like a grey card; the meter is doing its job.</p>

[clive_murray_white]

<p>Ah but Brooks - it's not under exposed, it was a black mirror and as I said at the beginning I thought that my camera would "assume" the black was 18% grey, Ellis said that meters have got a whole lot smarter these days. </p>

[bgelfand]

<p>Hi Clive,</p>

<p>I understand your point, but you are taking a picture of a reflective surface - one that reflects much more light then a grey card. It is not the color or the lightness of the reflective surface that is determining the exposure, but the reflection itself. The reflection of the background, which is what is being metered, is properly exposed; your face, camera, and body are underexposed (by design?). That is what I was referring to as underexposed.</p>

<p>When you are dealing with a reflective surface, the color of the surface is not the determining factor for exposure or even, within limits, color; it is the reflected image that determines exposure. Black mirror or white mirror, it should make no difference.</p>

<p>The mirror is not "lying"; it is doing its job of reflecting almost all the incident light. It is that incident light that determines exposure.</p>

[clive_murray_white]

<p>I think you've got it Brooks, the key was the reflected mid grey wall in the background or in truth a near white wall that had been darkened to look like mid grey by the either/both the black mirror and amount of available light.</p>

<p>The over and under expose debate is an interesting one, the picture above looks just like the reflection I saw, maybe we could call it a naturally underexposed scene ie its a dark room.</p>

<p> </p>

[bgelfand]

<p>Or maybe just call it a low key scene. Your hair, frame left, and hand as well as the wall, look properly exposed for a low key scene. And the white base of the stand behind you is also properly exposed for low key.</p>